If I may make a suggestion, try a N7VE SWR bridge. the design provides at least a measure of safety for the finals, then when your Antenna tuner is adjusted to satisfaction, switch the bridge out of circuit so your signal goes straight to the ATU and provides you (the operator) with a degree of confidence in it presenting a workable matching solution for the Radio. Worth noting that many of the kit QRP tuners have this arrangement already built in.
Just my $0.02 worth.
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QRP - ?EFFICIENCY AND SKILL, NOT POWER.?
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God Bless from Wayne Dillon - NQ0RP
Fate whispered to courageous "You cannot withstand the storm"